The desirability of large area shelters has long been recognized, and many industries employ pavilionlike shelters to protect against the elements, such as sun, wind and rain. These large area shelters are commonly used in commercial, fair, exhibit and party applications. One such example may be found in traveling shows and exhibits, such as merchandise exhibits, carnivals and the like.
Historically, large area tents are believed to have been first used by traveling shows, such as traveling circuses. These businesses found it necessary to employ large area tents as a staging arena for the circus activities. Yet another example of the need for large scale tents was early recognized by the military with its need for large area tent structures that could be rapidly erected and disassembled. More recently, merchants have implemented tent structures to provide additional space as a sheltered display area for their merchandise.
Despite the long felt need for large area tent structures, there has in the past been surprisingly little development in the industry of large sized tents. Examples of existing large area structures include the standard rectangular tent that has one or more apex portions supported by central poles; the perimeter of this tent covering is either supported by perimeter poles and with the peripheral edge of the tent being tensioned against a plurality of spikes or staked directly to the ground. Guy ropes are sometimes used to interconnect the perimeter to the stakes and block and tackle assemblies may be employed to tension the tent covering after it is erected. Another example of the traditional large area tent is the circus tent wherein margins of the tent are primarily stakes and center poles erected after which the apex portion of the tent is drawn up around the pole by means of pulleys; block and tackle assemblies are again employed to tension the circus tent against the stake elements.
In recent times, some efforts have been made again to create different tent structures which provide shelter and which are more aesthetically pleasing. These developments have, in part, stemmed from improvements of fabric technology, such as the development of lighter weight, stronger materials which more readily accept tension forces and which tend to better retain their shape under environmental conditions. However, even these recent tent designs often have relied on the old concept whereby the corners of the tent covering are individually and sequentially stressed against a constant length, erected center pole.
In response to the above described needs, I developed a new and useful tent structure which was both light weight and could be erected by a single person in a minimum amount of time. This tent structure is described in my U.S. Pat. No. 4,942,895 issued 24 Jul. 1990. In this construction, a pyramid shaped flexible covering is utilized, and the corner portions of this structure are first staked in a selected geometrical shape. An expandable center pole assembly is provided to position between the support surface and the vertex portion after staking the perimeter. The effective length of the center pole is then increased to raise the vertex portion away from the support surface thus uniformly applying tension to each of the anchored corner portions of the covering.
While existing large area tent structures are useful in sheltering an area against environmental elements, a disadvantage is found where a center pole construction is used. Thus, even though the tent structure described in my earlier patent provides significant advantages over prior art structures, the center pole design still hinders free movement of persons in the sheltered area and inhibits the arrangement of display cases, objects, tables, chairs and the like which are organized in a sheltered area.
It is recognized that the canopy and tent industry desires tent structures which are known as "clear-span" structures which avoid the use of a center pole construction. While small area clear-span structures are not difficult to achieve, large area, clear-span structures have been found to be difficult to construct due to the tension forces and weights of material between peripheral support poles. A further difficulty is found in constructing large, clear-span structures since rainwater tends to collect on the roof covering when a center pole is eliminated since an elevated apex located centrally of the structure cannot be obtained without a center pole. The weight of water collecting on the canopy roof can cause the covering to tear, collapse or otherwise fail in providing an adequate sheltered space.
Therefore, despite prior art structures, including that described in my own patent, there remains a need for large area clear-span tent structures which eliminate center pole supports. There is a further need for these clear-span structures to be relatively light weight yet which can be easily erected by one or a small number of persons. There is a further need for such a structure which can withstand environmental elements with reduced danger of failure.